I think the controlling factor on this discussion for adding or selling to get the needed length should really depend on the person's ability to actually modify the trailer. The trailer I referenced about adding 10 feet to it started out life as a flatbed trailer, in the 20-24 foot range. My brother's boss needed a car hauling trailer to haul two conversion vans behind an angle deck one ton truck. I added enough matching steel I-beam to make it 33 foot long. I wanted to add a third axle, but cost vetoed that. So I removed the front axle, added hangers behind the last one and moved the front to the rear. I also needed to be an dovetail trailer. This was all done and the last time I saw the trailer it looked like heck! It was being pulled by a new Dodge, so I asked the driver how many miles the Dodge had on it when it was replaced. 450,000 miles on the old one and the new one had 100,000 miles on it, and the trailer goes everywhere the truck goes. He said they lost the keys to the coupler lock and had to disconnect it by removing the hitch, so they just left it on. I went to G rated tires and all was well till they blew one and started buying tires on the road. Most tire shops only carry 10 ply tires in that size, so that is what was bought. The owner complained about how many tires he was having to buy and I told him why. His option, spend the money on G rated tires or add a third axle. He never did either, and ultimately went out of business because he couldn't make enough money.
David from jax